The present invention relates to a motor with a dynamic-pressure type bearing device, and is applicable particularly, but not exclusively, to a drive motor such as a spindle motor for use in a computer-related information processing apparatus such as a hard disc drive and a floppy disc drive which motor is required to have a high-speed rotation, a high rotational accuracy, a small vibration, a high rigidity and other operating characteristics.
Conventionally, a dynamic-pressure type bearing device is used as a bearing for a laser printer polygon mirror drive motor, VTR cylinder motor and the like, while a spindle motor with a dynamic-pressure type bearing device is not yet adopted for a hard disc drive, particularly below 3.5 inches, which is a computer-peripheral information storage unit of which a higher performance and a higher reliability are required. This is because the reliability such as a long lifetime of the dynamic-pressure type bearing device lacks concurrently with problems in structure, accuracy, cost and others. For example, difficulty is encountered to provide an appropriate axial-direction dynamic-pressure type bearing structure and while satisfying a requirement for rigidity against impact in the axial direction. Accordingly, the conventional spindle motor for the hard disc drive adopts a ball bearing. However, recently, in addition to requirements such as size-reduction, anti-impact, noise-reduction and long lifetime, in accordance with sharp increase in storage capacity and recording density the access speed is increased, thus requiring a high rotational accuracy and a high-speed operation. The conventional ball bearing cannot cope with these requirements.